Long line fishing is a widely practiced fishing technique that is used to catch large quantities of fish each year. Long line fishing involves setting very long fishing lines, in some instances up to 150 km in length, off a fishing boat. Each line may have hundreds or thousands of hooks suspended from a main line, with each hook being baited. As the main fishing line is fed off the rear of the boat, each baited hook slowly sinks through the water until it reaches its fishing depth. Long line fishing has proven to be an efficient technique for catching fish and as such forms an important role in feeding the world.
Although long line fishing is a very efficient technique for catching fish, it is unfortunately also responsible for the deaths of a very large number of seabirds and to a lesser extent, turtles, every year. In particular, seabirds, such as albatrosses, petrels and shearwaters are attracted to the long line fishing boats and dive for the baits as they are fed out from the rear of the fishing boat. Unfortunately, many seabirds become hooked by the hook to which the baits are attached in this process. Some studies have estimated that in excess of 300,000 seabirds die each year as a result of becoming hooked on long line fishing hooks. Typically, the seabirds dive for the bait, become hooked by the hooks and are drowned.
As well as being a conservation issue, it is also in the interest of the fishermen to avoid by-catch of seabirds. The by-catch of seabirds represents a loss of bait and hooks that could otherwise be used to catch fish. Furthermore, fisherman often utilise sightings of the seabirds to assist in location of the schools of fish that they are attempting to catch.
A number of conservation and government bodies as well as the fishing industry have provided recommendations on how to reduce by-catch of seabirds in long line fishing operations. These include:                Setting long line gear at night. Seabirds usually feed during the day. This has met resistance because it decreases fishing time;        Decrease lights that illuminate the water at night. The lights attract the birds and assist in helping the birds find the bait. Operating in darkened conditions represents an occupational health and safety issue;        Throw hooks into the water from the lee side of the boat. Hooks sink faster there than on the turbulent windward side;        Hauling gear as fast as possible and keep the line coming up at a steep angle to the surface;        Thaw bait completely because frozen bait floats;        Only use bait with deflated swim bladders, again to increase the speed at which the bait (and hook) sinks;        Use streamers to scare the birds away. Such streamers can be flown from the back of the boat over the areas where the long lines are being dropped;        Use weighted hooks & lines to help the hooks sink faster. This represents an occupational health and safety issue with lives being lost from the practice; and        Don't throw fish guts into the water before the long lines go into the water, wait until the lines are set.        
The above measures have been shown to have limited and sometimes minimal effect, increase costs, are hazardous and reduce fishing productivity.
By-catch of seabirds may also be a problem in other fishing operations that use hooks to catch the fish.